The rolling of long, metal products such as thin bars, ribbed bars, rod, wire or other similar products is known, which provides the progressive reduction in thickness of said metal products by means of cylinders, rolls or rotating rings in rolling stands located one after the other along a rolling axis.
In the last steps of the rolling process it is known to use, for example, one or more guide devices, each configured to guide and support the metal products on entering into or exiting from a rolling stand, to a finishing stand for example.
Such guide devices, examples of which are shown in EP 0.143.523 and in DE 1.602.071, are needed to keep the metal products, in particular when the thickness is reduced to a value of a few millimeters, in the correct working position in line with the gap defined between the rolls or rings.
The known guide devices each normally comprise at least a pair of guide rolls mounted on a support body and with axes of rotation orthogonal to the rolling axis.
The guide rolls are usually idle and kept constantly in contact with the products being rolled, from which they receive, by friction, the rotatory motion. The external surface in contact with the products being rolled can be flat or grooved.
Guide rolls are known made of one material, in a single piece, or made of two or more materials, in which a ring of a first material, hard and resistant to wear, is integrated with a core or hub made of a second material, normally less hard and lighter than the first material.
It is also known that each guide device includes a support structure to which the support body of the guide rolls is attached.
The function of the support structure is to support the support body and allow the stable attachment of the guide device in a desired position upstream or downstream of the corresponding rolling stand and in close proximity to the corresponding rolls or rings.
The products being rolled generally transit inside the guide device at high speeds, even up to about 150 m/s, and have temperatures that can be comprised between 800° C. and 1,100° C. for example.
As a consequence of the conditions reported above, it is necessary to make the guide rolls of such guide devices, at least in the part which is in contact with the metal products in transit, of materials that are hard and resistant to wear, for example ceramic materials with a carbide base.
It is also necessary to make the support body so that it is able to resist, for the entire duration of the rolling process, the high temperatures quoted above, without suffering macro- or micro-structural modifications. For this reason, the support body is normally made of steel, preferably stainless steel.
Moreover, it is necessary to make the support structure robust and resistant to mechanical stresses that originate during high-speed rolling and, at the same time, resistant to impacts or other stresses that occur in normal functioning, and also unforeseen ones. For this reason, the support structure is normally made of steel.
It is known that the guide devices are removed from their assembled position on the rolling line every time it is necessary to carry out maintenance, or to remove the scale that has been deposited during rolling, or to replace them after changing section or type of long metal product to be rolled.
One disadvantage of known guide devices is that they are heavy and require the assistance of mechanical lifting and moving arms for their removal, thus determining extended procedure times. This disadvantage can consequently lead to extended down-times for maintenance, with negative effects also on the overall production costs and overall productivity.
Moreover, heavy guide devices can be a source of risk for the operators since, if moved manually, they can cause accidents and/or occupational injuries, for example damage to the back or lumbar muscles of the operators.
Another disadvantage of known guide devices is that they have a heat conductivity such that the discharge of the heat accumulated during rolling, in particular in the parts nearest the product in transit, occurs with relatively long times, even up to a few dozen minutes after the end of rolling. This considerably delays the possibility of intervention of an operator with respect to the stopping of the plant, with consequent lengthening of intervention and maintenance times, and has a negative effect on the overall costs of the production process.
Moreover, an excessive accumulation of heat due to a relatively limited heat conductivity can have negative effects on the mechanical resistance of the material, if this is subjected to high temperatures for an excessively long time.
Furthermore, another disadvantage of known guide devices is that they are complex to make and they require long and costly operations to be produced, in particular because of the resistance and physical characteristics of steel.
In the field of rolling long products, these problems have never been looked at in their entirety, to find a solution that could provide the compromise for the different needs. It must also be taken into account that the problems connected to the high temperatures are verified in the increasingly high speeds at which the metal product is rolled, with the evolution of technology, even recent. Moreover, the problems linked to the weight of the guides, and thus linked to the risk of accidents and occupational injuries, are reflected in the evolution of legislation on safety in the workplace.
This explains the mental block of those working in this field against considering possible alternatives to steel in making this type of guide, since the above problems are not considered, and since until now steel has always been considered a material that can satisfy all the requirements of the normal functioning of this type of equipment.
Contrary to the operating tradition, now consolidated in this sector, and trying to find a solution to the new problems posed by the evolution of rolling technology both in terms of process and in terms of equipment, Applicant set himself the task of finding an alternative solution to using the standard, consolidated materials used in this sector, to overcome the disadvantages that have been created due to technological evolution and developments.
One purpose of the present invention is therefore to make a guide device for long metal products, associable to rolling stands of the type with cylinders, rolls or rings, which can be removed quickly and easily for maintenance or replacement, and which therefore allows to reduce the down-times, speeding up the production process in its entirety.
Another purpose of the present invention is to make a guide device that is light, easy to move, even manually by an operator without needing to use lifting and moving means. A light guide device can also allow to reduce the physical efforts that an operator must perform in order to move it manually, which all means a reduction in the risk of accidents and occupational injuries, for example to the back or lumbar muscles of the operator. This advantageously allows to reduce the absences of the operator from work because of accidents or injuries, as well as to satisfy any possible legislation on safety at work currently in force.
It is also a purpose of the present invention to make a guide device that is resistant mechanically and able to discharge rapidly the heat accumulated during the rolling process, making the intervention times quicker at the end of a corresponding rolling pass.
Another purpose of the present invention is to make a guide device that, to be produced, needs less time and less complex and costly mechanical workings than those used in the state of the art.
The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.